Cardiovascular Health: Blood and Its Functions

• These notes are about cardiovascular health

Blood

• The cardiovascular system comprises blood, interconnected tubes (blood vessels), and the heart
• The heart pumps blood through blood vessels
• The circulatory system is a closed system
• It includes blood, the heart, and blood vessels
• Blood is the only fluid tissue
• It appears as a uniform liquid, but consists of specialized cells suspended in a unique organic liquid solution
• Blood cell suspension and dispersion depend on circulation
• Blood clots if not in motion
• If cells are not disbursed correctly the entire cardiovascular system can fail
• Failure can lead to organ failure
• Blood is the life-sustaining transport vehicle of the cardiovascular system

Blood's Functions

• Blood functions include:
  • Transport: Delivers O2 and nutrients, carries metabolic wastes, and shuttles hormones
  • Regulation: Maintains body temperature, pH levels, and fluid volume
  • Protection: Prevents blood loss and infection, and carries immunity agents
• Blood is a type of connective tissue
  • Its matrix is a nonliving fluid called plasma, with living blood cells called formed elements suspended in it
  • Formed elements are cells inside of blood

Components of Blood

• Erythrocytes are red blood cells that make up 99% of blood cells and carry oxygen and carbon dioxide
• Leukocytes are white blood cells that fight against infection and cancer and are part of the immune system
• Platelets are cell fragments essential for proper blood clotting
• A spun tube of blood yields three layers:
  • Plasma (~55%) on top
  • Buffy coat (<1%) in the middle (WBCs and platelets)
  • Erythrocytes (~45%) on the bottom
• Hematocrit is the percent of blood volume that is RBCs
• Normal values:
  • Males: 45% ± 5%
  • Females: 42% ± 5%
• Blood is a sticky, opaque fluid with a metallic taste.
  • Color varies with O2 content (scarlet red with high O2, dark red with low O2)
  • pH 7.35-7.45
  • Makes up ~8% of body weight
  • Average volume: 5-6 L in males, 4-5 L in females

Blood Plasma

• Plasma is the liquid component of blood
• A straw-colored and viscous fluid that contains organic and inorganic substances and proteins dissolved in water
• Largely because of normal, continuous RBC breakdown
• Hemoglobin release and breakdown creates “free bilirubin”
• Major Plasma Contents Include Include H2O (93% by weight) and Proteins (7% by weight)
• Remaining substances have negligible weight, but relatively high concentrations
• Gases, electrolytes, nutrients, waste products, and hormones

Plasma Proteins

• Albumins are the most abundant type of protein in blood, synthesized in the liver
  • Are non-penetrating proteins that bind and transport important substances
• Globulins are less abundant and larger, but have similar functions to albumins
• Fibrinogen is for blood clotting
  • It becomes fibrin proteins that create a mesh screen for platelets to stick to and form a blood clot
• Plasma proteins maintain water balance between blood and tissues via osmotic pressure
• Electrolytes maintain blood pH and osmotic pressure
• Plasma can be separated from blood cells
• Average sized adult has 5.5 L of circulating blood, and 45% is RBCs

Erythrocytes

• This measurement is called the hematocrit level
• They function in transporting molecules
• Oxygen received through lungs
• Carbon dioxide produced by cells
• Contain the protein HEMOGLOBIN which can bind both O2 and CO2 molecules
  • Heme (= iron Fe) creates red pigment in blood
• O2 moves in and out of the RBC by simple diffusion
• Erythropoiesis is the process by which the origin, development and maturation of erythrocytes occur
• They possess a biconcave disk shape with 7µm in diameter
  • High surface-to-volume ratio for rapid diffusion
  • Very flexible membrane and membrane
  • membrane proteins define blood type

Erythrocyte Produciton

• Created w red bone marrow
• Key nutrients required to make red blood cells, they have a short lifespan
• Immature blood cells produce hemoglobin and contain ribosomes inside
  • Must release mature blood cells in circulation
  • Immature cells in circulation can mean a large problem like cancer
• Lose nuclei and organelles at maturity for a ~120 day lifespan
• Cannot reproduce because they don't have organelles
• Erythrocytes are dedicated to respiratory gas transport meaning that hemoglobin binds reversibly with oxygen
• Normal lab values for hemoglobin:
  • Males: 13-18g / 100 ml
  • Females 12-15g/100 ml
• Each hemoglobin can transport 4 Oxygen molecules, Each RBC contains 250 hemoglobin millions
  • Oxygen loading produces oxyhemoglobin (ruby red blood)
  • Oxygen unloading in body tissue produces deoxyhemoglobin (dark red/maroon)
• Carbon dioxide loading produces carbaminohemoglobin
• Need Amino acids, lipids, Carbohydrates, iron, Folic Acid (vitamin B9), Vitamin B12 (cobalamin)
• Iron is the element that oxygen binds with inside hemoglobin molecule
  • 50% contained in the RBCs and 25% stored in liver as ferritin
  • Helps with iron deficiency
• Deficiency can happen if not absorbed properly

Vitamin B9 and B12

• Vitamin B9 is critical for proper DNA formation and cell division
  • Deficiency causes = less RBC production
  • Found in: green leafy veggies, yeast, liver
• Vitamin B12: only found in animal products(nutritional yeast)
  • Required to absorb B12 from digestive tract
  • Critical for formation of myelin sheath on nerve cells
• Regulation of Erythrocyte Production is stimulated by erythropoietin (EPO) by the kidneys

Anemia

• Anemia is a reduced ability of the blood to carry oxygen
  • Insufficient number of erythrocytes
  • Decreased hemoglobin saturation of RBCs
  • Combination of both
• Microcytosis causes small cells and often iron deficiency
• Normocytosis causes normal cells and is caused be blood loss
• Macrocytosis causes causes enlarged cells and is caused delayed cell division from a B9 or B12 Deficiency
• Polycythemia is opposite of anemia
  • Hallmark of this disease is a significant increase in the number of RBCs in the blood
  • Neoplastic Profliferation

Leukocytes

• Leukocytes have 5 major types:
  • Eosinophils, Basophils, Neutrophils, Monocytes, Lymphocytes
  • Each one is produced in the bone marrow
  • Last two develop further of of marrow
  • Each type has specific immune defensive capabilities
• Platelets are fragments of Megakaryocytes that produce platelets in blood
  • Imperative for clotting through activated platelet aggregation
• Regulation of red blood cell
  • Blood cell production is highly regulated by the bod, chemical, signaling and Growth factors

Heart Design

• Efficient Movement of Blood needs rapid flow
  • Heart must provide speedy pumping pressure that Simultaneously moves all blood in the system at the same time
  • Blood flow direction should be in one primary direction from/to the hear
• Blood vessels have an immense degree of branching and converging, must create a circulatory pattern
• Small/large ranges of branching vessels ensure close blood flow proximity and most cells are few cell diameters away from capillary blood vessel source
• A simple heart is a “Four-chambered” muscle halves
• The Cardiac Muscle has:
  • A right and left half which each half has two chambers, one upper (atria) and one lower (ventricles) All ATRIA receive blood returning to the heart, then deposit blood into their respective VENTRICLES through “valves” Atria are minor pumping chambers of the heart

Primary Circuits

• The primary circuits stem from the heart creating cardiorespiratory System:
  • Pulmonary circuit: Where blood pumps through the RIGHT side of the heart
    • Deoxygenated blood becomes oxygenated and CO2 is then released
  • Systemic circuit: Where blood pumps through the LEFT side of the heart
    • Oxygenated blood becomes deoxygenated and carbon dioxide is then gathered

Vessels Needed

• Arteries always carry blood AWAY from the heart
• Veins always carry blood TOWARDS the heart
• Capillaries transition Arteries to Veins
  • Provide gas, nutrient and waste exchange

Heart Walls

• The heart has three layers:
  • Epicardium is the external layer
  • Myocardium is the middle layer consisting of contractile Muscle cells
  • Endocardium: innermost layer with function to be smooth
• Internal Chambers and Septa has four internal chambers
  • Two superior atria and two inferior ventricles
  • interatrial/ventricular septum
  • Fossa ovalis is a remnant of fetal heart

Atrial/Ventricular Chambers

• Atria have receiving chambers with small, thin-walled chambers with auricles that increase atrial volume
  • They receive deoxygenated and oxygenated blood
• Ventricles have discharging chambers that that make up most of the volume of heart
  • Right ventricle is the most anterior surface
  • Left ventricle is the is posteroinferior surface

Blood Vessel Structure

• Blood vessels are delivery systems for all dynamic structures that begin/end at the heart , capillaries give cells direct contact for needs
• All vessels consist of a lumen in the center, surrounded by 3 tunics
• The larger the lumen is the larger the vessel
• Tunica intima is in “intimate” contact with blood and innermost layer is made of endothelial cells
  • Slick surface that reduces friction.
• Tunica media is in the mostly smooth muscle
• Middle layer and sheets of elastin
• Bulkiest layer responsible for maintaining blood flow and blood pressure Tunica externa is the outermost layer, tunica adventitia that composed mostly of loose collagen fibers that protect and reinforce wall for surrounding structures

Arteries

• Can be elastic or muscular
  • Elastic arteries help with blood flow, known to be “conducting arteries”
  • Thick walled with large lumens (aorta and branches)
  • Contain elastin
• Muscular arteries give rise tomuscular arteries known as “distributing arteries” deliver blood to body organs
• They contain named arteries ranging “pinky sized to pencil sized”
  • Thickest media with smooth muscle

Capillaries and Veins

• They make up arterioles: smallest all arteries where control the flow of blood into capillary beds
• Capillaries microscopic for gasses, nutrients, wastes, and hormones in blood
  • There are continuous, fenestrated and sinusoidal capillaries
• Capillary Beds, is inter woven network of capillaries where microcirculation flow:
  • Terminal Arteriole ->Capillary bed -> Post capillary venule
• Veins that are elastic and carry blood back to the heart where formation then becomes bigger and bigger
  • Capillary: Small - Middle sized Veins: Large - Heart
  • Veins have tunics, but thinner w large lumens due to holding 65%

Vessel Pressure

• Pressure: Blood pressure is lower in vessels, adaptations ensure return of blood from valves to heart
• Clinical that contributes varicose: Elevated venous pressure
• The Force generated by the pressure of blood in the inner, the heart's pumping as the heart and can be measured with mercury/Units mmHg
• Systemic circulation has greater pressure than pulmonary
• Resistance is difficult for blood to flow, measurement of friction!
  • Resistance is increased by decreased radius, longer vessels , blood viscosity ecosity

Blood Flow

• Flow: Blood moves from high to low pressure Is very efficient for blood
• laminar Blood flows smoothly/linearly through continuous layers, decreases the energy required to push forward and reduce micro damages (turbulent can rupture RBC)

Heart Mechanics

• Heart has pericardium that protects (clinically is tamponade) ,
• Myocardium is an important muscle for contraction and contains endothelial cells in its interior
  • Has thick ventricular walls
• Contractions gives changes in blood which causes communication to the blood
• ATRIOVENTRICULAR VALVES: designed to give forward movement
  • Made of endothelium
• Electric communication that requires depolarizations should to lead to contractions
  • There is an electrical impulse that travels through muscle
• The heart beats electrical currents without outside signals, so needs an automatic nerve censor that monitors hemodynamics, or heart pressure and chemicals
• The muscles send feedback and respond the signals!

Conduction

• Cardiac Myocytes must beat tight together and fast which requires the muscle cells to connect and squeeze (1% for contractivity)
• Important for pumping efficiently where rate is controlled with factors
• The pacemaker cells have unstable resting membrane potentials and has charges regulated with the ion concentration
• 3 steps:
  • Sodium enters and becomes +
  • Calcium open, become excited
  • K Exits where cells become more -
• Pacemaker of heart is SINOTRIAL = 75 times/ Min
• Defects in the machine: heart irregular , fibril contractions, cardiac death
• Sinoatrial node is defective can be ectopic focus with Av junctional =45/60 minute triggers the SA node , and heart fills takes over

Cardiac Muscle

• Actual squeeze and force must be excited where action potential excites electrical charge
• The heat of blood is measured through electrocardiography
  • Detected electrical currents generated by heart with 𝒪 , 𝒩 are electric components (see notes for details

Heart Anatomy

• Cardiocytes are connected with a nonconducting (tissue doesn't travel), and the AV bundle can't travel through it so impulses from the bottom chamber
• Impulses requires bilateral ventricular contractions and Adult are rates BPM with the nerve
• The heart contains sympathetic (Flight) or Parasympathetic nerves (rest) that release transmitters
• The blood that is inside wont fee tissues in the Cardiac chamber so needs the blood to perfuse,
• Coronary arteries return to blood in rt auricle

Cardiac Cycle

• The mechanical events of the heart are cycled. A cardiac cycle contains period during one beat lasting .8 is ventricular

• 2 phases for systole where pressure rises blood pumps, for diastole Chamber falls,

• The two sounds are hear in the heart

  • First sounds are the S2/ dup = ventricular ejection w closures in valves High pitches

• CO or cardiac output, is the rate of blood volume -HR Stroke equals to SV= HR beats x SV

• SV and End D Volume effects the length of ventricular

• Main of heart

  • Preload is the degree of stretch of muscles for best muscle at given length
  • Afterload is the pressure ventricles use eject blood

• Hypertension and stress can lead to squeeze with High ESV decreased S